Snowmobile

ABSTRACT

A snowmobile includes a frame having side walls and a support platform. The side walls cooperate with the support platform to define a tunnel. The snowmobile further includes an endless belt assembly supported by the frame, a motor supported by the frame, and a running board removably coupled to the tunnel.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.13/773,326, filed on Feb. 21, 2013, which is a continuation of U.S.application Ser. No. 12/782,363, filed on May 18, 2010, now U.S. Pat.No. 8,381,857, which is a continuation-in-part of U.S. application Ser.No. 11/501,456, filed on Aug. 9, 2006, now abandoned, the disclosures ofwhich are expressly incorporated by reference herein.

BACKGROUND AND SUMMARY

The present invention generally relates to snowmobiles. Moreparticularly, the present invention relates to the components of asnowmobile such as the frame, skis, motor, and endless belt assembly.

Generally, there are a variety of configurations of snowmobilesavailable for applications such as deep snow, high performance, luxurytouring, trail riding, etc. Most snowmobiles include a frame, a motor, apair of front skis, and an endless belt assembly. Typically, featuressuch as engine displacement and track length vary depending upon thespecific application for which the snowmobile is targeted. For example,snowmobiles designed primarily for deep snow application may include anendless belt assembly having a longer track length, i.e. 166 inches,than a snowmobile designed primarily for trail riding, i.e. 135 inches.A snowmobile designed for deep snow may also include a relatively largedisplacement engine, i.e. 900 cc³, to provide suitable power whenoperating in a mountain environment at higher elevations with lessoxygen. Other features of a deep snow snowmobile may be added to improveride and handling characteristics such as side hilling.

One illustrative embodiment of the present disclosure includes asnowmobile comprising a frame, a motor supported by the frame, anendless belt assembly supported by the frame, a pair of steering spindleoperably coupled to the frame, and a pair of front skis operably coupledto the steering spindle, each of the front skis including upper andlower surfaces, the lower surfaces including a runner, the uppersurfaces including a plurality of projections adapted to providetraction to an operator.

Another illustrative embodiment of the present disclosure includes asnowmobile comprising a frame, a motor supported by the frame, anendless belt assembly supported by the frame, a pair of steering armsoperably coupled to the frame, and a pair of front skis operably coupledto the steering arms, each of the front skis including front and rearends and inner and outer edges, the outer edge of the rear end of eachski including a notch.

Yet another illustrative embodiment of the present disclosure includes asnowmobile comprising a frame, a motor supported by the frame, anendless belt assembly supported by the frame, a pair of steering armsoperably coupled to the frame, and a pair of front skis operably coupledto the steering arms, each of the front skis including front and rearends and inner and outer edges, the inner and outer edge of the rear endof each ski including a notch.

Another embodiment of the present disclosure includes a snowmobilecomprising a frame assembly including a steering hoop structure and atunnel, the tunnel including a center plate and first and second sidepanels, the steering hoop structure coupled to the first and second sidepanels and extending above the tunnel, the first and second side panelseach including a running board supported by the steering hoop structure,the steering hoop structure including a toe clip positioned adjacent toeach of the running boards, a steering assembly supported by thesteering hoop structure, a motor supported by the frame, and an endlessbelt assembly supported by the frame.

According to another illustrated embodiment of the present disclosure, aski for a snowmobile includes a body portion having an upper surface anda lower surface, a keel formed on the lower surface, at least onelongitudinally extending rib extending upwardly from the upper surface,and a plurality of projections arranged side by side and extendingupwardly from a top edge of the at least one longitudinally extendingrib. The plurality of projections are configured to provide traction toan operator.

According to yet another illustrated embodiment of the presentdisclosure, a ski for a snowmobile includes a body portion having anupper surface and a lower surface having a planar bottom portion. Thebody portion has a front end and a rear end establishing a lengthdimension of the ski and an inner edge and an outer edge establishing awidth dimension of the ski. At least one of the inner edge and the outeredge of the rear end of the body portion includes a notched portionhaving a notch length dimension of at least one sixth of the lengthdimension of the ski and a notch width dimension of at least one fifthof the width dimension of the ski.

The above mentioned and other features of this invention, and the mannerof attaining them, will become more apparent and the invention itselfwill be better understood by reference to the following description ofembodiments of the invention taken in conjunction with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an illustrative embodiment snowmobile;

FIG. 2 is a perspective view of one embodiment of an integral frame andtunnel system of the snowmobile shown in FIG. 1;

FIG. 3 is an exploded view of the left side of the integral frame andtunnel assembly shown in FIG. 2;

FIG. 4 is an exploded view of the right side of the integral frame andtunnel assembly shown in FIGS. 2 and 3;

FIG. 5 is a perspective view of the front end of the integral frame andtunnel assembly shown in FIGS. 2-4;

FIG. 6 is a partial view of one embodiment of a running board of thesnowmobile shown in FIG. 1;

FIG. 7 is a perspective view of one embodiment of a tunnel assembly ofthe snowmobile shown in FIG. 1;

FIG. 8 is an exploded view of the tunnel assembly shown in FIG. 7;

FIG. 9 is a bottom view of the tunnel assembly shown in FIGS. 7 and 8;

FIG. 10 is cross-sectional view of the rear end of the tunnel assemblyshown in FIGS. 7-9;

FIG. 11 is a cross-sectional view taken across a middle section of thetunnel assembly shown in FIGS. 7-10;

FIG. 12 is a cross-sectional view taken across a section of onecomponent of the heat exchanger shown in FIGS. 1-11;

FIG. 13 is a cross-sectional view of an alternative embodiment heatexchanger similar to the heat exchanger shown in FIG. 12;

FIG. 14 is an exploded view of another embodiment of a tunnel assemblythat may be used in a snowmobile such as the one shown in FIG. 1;

FIG. 15 is a perspective view of the bottom side of the tunnel assemblyshown in FIG. 14;

FIG. 16 is an exploded view of another embodiment of a tunnel assemblythat may be used in a snowmobile such as the one shown in FIG. 1;

FIG. 17 is a perspective view of the bottom side of the tunnel assemblyshown in FIG. 16;

FIG. 18 is a cross-sectional view taken across a middle section of thetunnel assembly shown in FIGS. 16 and 17;

FIG. 19 is a cross-sectional view taken across a middle section of thetunnel assembly shown in FIGS. 14 and 15;

FIG. 20 is a cross-sectional view taken longitudinally across the rearportion of the tunnel assembly shown in FIGS. 16-18;

FIG. 21 is a partial perspective view of one embodiment of a drivesystem of the snowmobile shown in FIG. 1;

FIG. 22 is a partial perspective view of one embodiment of an endlessbelt assembly of the snowmobile shown in FIG. 1;

FIG. 23 is a partial profile view of the endless belt assembly shown inFIGS. 21 and 22;

FIG. 24 is a partial profile view of the drive system of the endlessbelt assembly shown in FIGS. 21-23;

FIG. 25 is a partial top view of the belt of the endless belt driveshown in FIGS. 21-24;

FIG. 26 is a partial perspective view of the rear end of the endlessbelt assembly shown in the FIGS. 22 and 23;

FIG. 27 is a perspective view of one embodiment of an air intake systemof the snowmobile shown in FIG. 1;

FIG. 28 is a partial top view of the air intake system shown in FIG. 27;

FIG. 29 is a partial exploded view of the air intake system shown inFIGS. 27 and 28;

FIG. 30 is a profile view of the air intake system shown in the FIGS.27-29 with the movement of the expandable section shown in phantom;

FIG. 31 is a partial perspective view of one embodiment of a front skion the left side of the snowmobile shown in FIG. 1;

FIG. 32 is a profile view of the front ski shown in FIG. 31;

FIG. 33 is a bottom side view of the front ski shown in FIGS. 31 and 32;

FIG. 34 is a front view of the front ski shown in FIGS. 31-33;

FIG. 35 is a perspective view of the top side of the front ski shown inFIGS. 31-34;

FIG. 36 is a perspective view of another embodiment of a front ski thatmay be positioned on either side of the snowmobile shown in FIG. 1; and

FIG. 37 is a perspective view of another embodiment of a front ski thatmay be positioned on the either side of the snowmobile shown in FIG. 1.

Corresponding reference characters indicate corresponding partsthroughout the several views. Although the drawings representembodiments of the present invention, the drawings are not necessarilyto scale and certain features may be exaggerated in order to betterillustrate and explain the present invention.

DETAILED DESCRIPTION OF THE DRAWINGS

The embodiments disclosed below are not intended to be exhaustive or tolimit the invention to the precise forms disclosed in the followingdetailed description. Rather, the embodiments are chosen and describedso that others skilled in the art may utilize their teachings. Forexample, while the following description refers primarily to asnowmobile, it should be understood that the principles of the inventionapply equally to other snow vehicles. While the present inventionprimarily involves a snowmobile, it should be understood, however, thatthe invention may have application to other types of vehicles, such asmotorcycles, ATVs, utility vehicles, scooters, and mopeds.

Referring to FIG. 1, one illustrative embodiment of a snowmobile 10 isshown. Snowmobile 10 includes endless belt assembly 12, seat assembly14, hood 16, steering assembly 17, front skis 18, frame 20, and steeringarms 22. Steering assembly 17 is operably coupled to steering arms 22and allows a rider to steer snowmobile 10. A motor, not shown, iscovered by hood 16 and provides power to endless belt assembly 12.

Referring now to FIG. 2, tunnel assembly 22 and integrated steering hoopassembly 24 of frame 20 are shown. Steering hoop assembly 24 supportssteering assembly 17 of snowmobile 10 and provides structural support tosnowmobile 10. Steering hoop assembly 24 also provides attachment pointsfor body panels such as the hood. Additionally, steering hoop assembly24 provides lateral support in the event of snowmobile roll-over andprevents or reduces body panel collapse. Steering hoop assembly 24includes inner hoop 26 and outer hoop extensions 28 and 30. Inner hoop26 extends around the motor of snowmobile 10. Referring now to thecomponents on the left side of frame 20, best shown in FIG. 3, an upperend of outer hoop 28 couples to inner hoop 26. A lower end of outer hoop28 couples to longitudinally extending tube 42. Additionally, extension40 extends rearwardly from the lower end of outer hoop 28. Extension 40is coupled to one end of tube 44. The opposing end of tube 44 is coupledto inner hoop 26.

Console side 36 is coupled to inner hoop 26 and outer hoop 28. Consoleside 36 includes louvered portion 38 and lower portion 35. Both louveredportion 38 and lower portion 35 allow heated air from the enginecompartment under hood 16 to exit the engine compartment and provideheat to a rider's leg and boot. Lower portion 35 is coupled to runningboard 46. In this embodiment, running board 46 is integral with sidepanel 52 of tunnel assembly 22, however running board 46 may be aseparate component. Outer edge 76 of running board 46 is supported bylongitudinally extending tube 42 substantially along the length ofrunning board 46. Longitudinally extending tube 42 includes offsetportion 48 and bracket 50 which is coupled to side panel 52 of tunnel22.

Referring now to FIG. 4, the components of the right side of frame 20 isshown. The components on the right side of frame 20 are in a similararrangement and compliment the components on the left side of frame 20.Outer hoop 30 is coupled on an upper end to inner hoop 26. A lower endof outer hoop 30 is coupled to longitudinally extending tube 62. Thelower end of outer tube 30 also includes extension 60 which is coupledto one end of tube 54. The opposing end of tube 54 is coupled to innerhoop 26. Console side 32 is coupled to outer hoop 30 and includeslouvered portion 34 and lower portion 37. Louvered portion 34 is similarto louvered portion 38 of console side 36. Lower portion 37 of consoleside 32 couples to running board 64 which, in this embodiment, isintegral with side panel 58 of tunnel 22.

Running board 64 includes outer edge 63 which is supported bylongitudinally extending tube 62. Longitudinally extending tube 62includes offset portion 68 and bracket 70 which couples to side panel 58of tunnel 22. Offset portions 48 and 68 of longitudinally extendingtubes 42 and 62 may be used as handle portions by snowmobile operator.Offset portions 48 and 68 extend upwardly and rearward to bracket 70 toprovide the rider with a handle that is generally perpendicular torunning board 64. Additionally, tube 56 which is coupled on a first endto a rear section of side panel 52 and on a second end to a rear portionof side panel 58 may be used as a handle portion by a snowmobileoperator.

Referring now to FIGS. 1 and 5, a rider positioned on seat assembly 14has a boot positioned on each running board 46 and 63. The rider's bootsare positioned substantially below tubes 44 and 54 of integral steeringhoop assembly 24. In this orientation, a rider may contact or hook thetoe of each boot under tubes 44 and 54 to maintain balance or control ofsnowmobile 10 during snowmobiling.

Referring now to FIG. 6, a partial section of one embodiment of runningboard 46 is shown. In this embodiment, running board 46 includes aplurality of apertures 72 adapted to allow snow and ice from a rider'sboot to pass through and a plurality of extensions 74 to engage arider's boot. In this embodiment, apertures 72 a substantially flat toallows snow and water collected on running board 46 to exit.Additionally, running board 46 includes a plurality of offsetprojections 78 on outer edge 76. Offset projection 78 have an angularorientation relative to a longitudinal axis of running board 46. Theangular orientation of projections 78 or skewed relationship ofprojections 78 to the running board 46 provides traction to a rider'sboot. In this embodiment of snowmobile 10, running board 63 alsoincludes the features of running board 46 described above. It should benoted that any suitable arrangement of drainage apertures and/ortraction devices may be used on running boards 46 and 63 of snowmobile10.

Referring now to FIG. 7, a profile view of tunnel 22 is shown. As shownin FIG. 1, tunnel 22 extends over endless belt assembly 12 and preventssnow and ice from contacting the rider positioned on seating assembly14. Tunnel 22 includes side panel 52, heat exchanger 82, center panel80, heat exchanger 86, and side panel 58. Heat exchangers 82 and 86 arecoupled to the center panel 80 to form the top surface of tunnel 22.Side panel 52 is coupled to heat exchanger 82 to form the left side oftunnel 22 and side panel 58 is coupled to heat exchanger 86 to form theright side of heat exchanger 22. Bracket 102 is coupled to the rear endof heat exchangers 82 and 86 and may support a flap of material such asrubber to prevent snow from being thrown on the back of the rider. Heatexchanger 82 includes input 84 and plurality of channels 94 formedtherein. Similarly, heat exchanger 86 includes output 88 and pluralityof channels 96 formed therein.

Coolant from the motor of snowmobile 10 flows into inlet 84 and travelsthrough heat exchangers 82 and 86 before exiting through output 88. Inthe illustrative embodiment, inlet 84 and output 88 are positioned on anend of tunnel 22, however they may be positioned at any suitableposition along the longitudinal length of tunnel 22. Endless trackassembly 12, which is positioned below tunnel 22, throws snow and iceupward to contact heat exchangers 82 and 86. The snow and ice provideand cooling effect for the coolant as is passes through heat exchangers82 and 86. At the same time, heat from heat exchangers 82 and 86 preventsnow and ice build-up and packing under tunnel 22. In this embodiment,heat exchangers 82 and 84 are formed from extruded aluminum. However,any suitable material and method of construction may be used.

Referring now to FIGS. 8 through 10, end caps 100 are coupled to eachend of heat exchangers 82 and 86 to seal channels 94 and 96respectively, the rear end of heat exchangers 82 and 86 is coupled toconducting duct 98. Conducting duct 98 allows fluid to pass from heatexchanger 82 to heat exchanger 86. In operation, heated coolant from themotor enters heat exchanger 82 through inlet 84 and flows throughchannels 94 to conducting duct 98. The coolant is then directed to therear end of heat exchanger 86 and passes through channels 96 exitingheat exchanger 86 at outlet 88 and returning to the motor of snowmobile10.

Referring now to FIG. 11, heat exchanger 82 includes a lower extension83 and a flange 104 extending the longitudinal length of heat exchanger82. As shown, the top edge of side panel 52 is adapted to be positionedbetween lower extension 83 and flange 104. Side panel 52 may be securedin this position by adhesive, rivets, machine screws, bolt, anycombination thereof, or any other suitable fastener. Similarly, sidepanel 86 includes lower extension 92 and flange 102 which extend theentire longitudinal length of heat exchanger 86. Side panel 58 isadapted to be positioned between flange 102 and lower extension 92. Sidepanel 58 may be coupled to heat exchanger 86 by adhesive rivets, machinescrews, bolt, any combination thereof, or any other suitable fastener.In a similar fashion, center panel 80 is coupled between heat exchangers82 and 86. Heat exchanger 82 includes lateral extension 81 and lateralflange 77 extending the longitudinal length of heat exchanger 82. Oneedge of center panel 80 is positioned between lateral extension 81 andlateral flange 77. Heat exchanger 86 includes also includes lateralextension 85 and lateral flange 87. The opposing edge of center panel 80is secured between lateral extension 85 and flange 87. Center panel 80may be secured to heat exchangers 82 and 86 by adhesive, rivets, machinescrews, bolt, any combination thereof, or any other suitable fastener.It should be noted that the width of center panel 80 may be varied toproduce a tunnel having any suitable width. Additionally, in thisembodiment, tunnel 22 is a modular design and may be constructed to anysuitable length. In other embodiments, center panel 80 may be eliminatedand heat exchangers 82 and 86 may be coupled directly together.

Referring now to FIG. 12, heat exchangers 82 and 86 also includelongitudinally extending slots or recesses 79 and 90, respectively.Slots 79 and 90 provide a tunnel top attachment feature positioned alongthe longitudinal axis of the snowmobile. It should be noted that slots79 and 90 may extend along the entire length of tunnel 22 or may extendonly partially along the length of tunnel 22. Additionally, slots 79 and90 may be positioned anywhere on the outer periphery of tunnel 22, suchas the in or on side panels 52 and 58. Slots 79 and 90 are adapted toreceive a fastener that may be used to secure accessories, handles, toolkits, or any other suitable item to tunnel 22. In this embodiment, slots79 and 90 are integral to the tunnel assembly and prevent the need toany mounting holes or apertures in the tunnel assembly, which may weakenthe tunnel assembly. In this embodiment, slots 79 and 90 aresubstantially inverted T-shapes, however, any suitably shaped slot maybe used.

An alternative embodiment of slots 79, 90 is shown in FIG. 13. Heatexchanger 300 is similar to heat exchanger 82 with the exception thatslot 312 is formed in recess 314 of channel 302 so that the top surfaceof slot 312 is flat or coplanar with the later extension 308. Slots 79and 312 are inverted T-shaped slots, however any suitable shaped slotmay be used. Additionally, an upwardly extending protrusion such as aT-shaped protrusion may be used instead of or in combination with a slotto provide an attachment surface. In other embodiments, a plateincluding a longitudinally extending slot and/or protrusion may beaffixed to the top of the tunnel to provide an attachment feature abovethe tunnel of a snowmobile. In yet another embodiment, slots orprotrusions may be integral with or attached to side panels 52 and/or 58to provide attachment features. Another method of providing attachmentfeatures is described in U.S. Pat. No. 7,055,454, which is expresslyincorporated by reference herein.

Referring now to FIGS. 14 and 15, an alternative embodiment of thetunnel assembly for in FIGS. 7-11 is shown. Tunnel assembly 316 includestunnel 318 which is formed by a single sheet of metal and includes sidepanels 322 and 324 and center panel 320. Center panel 318 includes inlet330 and outlet 328 which are coupled to the liquid cooling system of thesnowmobile, as discussed above. Tunnel assembly 316 also includes lowerpanel 326. Lower panel 326 includes channels 332 and 334, end channel335, and center section 336. Lower panel 326 is coupled to the bottomside of center panel 318 to form a heat exchanger similar to the onedescribed in FIGS. 7-11. A cross-sectional view is shown in FIG. 19.Coolant enters inlet 300 and flows down channel 332 to end channel 335.The coolant then flows from end channel 335 to channel 334 and to outlet328. Center section 336 is also coupled to the lower side of centerpanel 318 to separate channels 332 and 334. Channels 332 and 334 mayinclude a plurality of surfaces adapted to improve the heat transfercharacteristics of tunnel assembly 316. Lower panel 326 may be coupledto center panel 318 by an adhesive, welding, or any other suitablemethod of attachment. It should be noted that inlet 330 and outlet 328may be reversed.

Referring now to FIGS. 16 and 17, another embodiment of a tunnelassembly is shown. Tunnel assembly 340 includes tunnel 342 which isformed by a single sheet of metal and includes side panels 346 and 348and center panel 344. Center panel 344 includes inlet 352 and outlet 350which are coupled to the liquid cooling system of the snowmobile, asdiscussed above. Tunnel assembly 340 also includes lower panel 354.Lower panel 354 includes channels 356 and 358, end channel 357, andcenter section 360. Lower panel 354 is coupled to the bottom side ofcenter panel 344 to form a heat exchanger similar to the one describedabove in FIGS. 14 and 15. A cross-sectional view taken along a middleportion of the tunnel assembly 340 is shown in FIG. 18. Additionally, across-sectional view taken longitudinally along the back section oftunnel assembly 340 is shown in FIG. 20. Coolant enters inlet 352 andflows down channel 356 to end channel 357. The coolant then flows fromend channel 357 to channel 358 and to outlet 350. Center section 360 isalso coupled to the lower side of center panel 344 to separate channels356 and 358. Channels 356 and 358 may include a plurality of surfacesadapted to improve the heat transfer characteristics of tunnel assembly340. Lower panel 354 may be coupled to center panel 344 by an adhesive,welding, or any other suitable method of attachment. It should be notedthat inlet 352 and outlet 350 may be reversed.

Referring now to FIG. 21, a partial profile view of drive system 124 ofendless belt assembly 12 is shown, endless belt assembly 12 includes apair of lower rails 110, a pair of front links 114, and a shock absorber120 as well as various other components (not shown). Lower rails 110 arecoupled together by cross shaft 112. Front links 114 are coupledtogether by cross shaft 116. Cross shaft 116 is also coupled to shockabsorber 120. Lower rails 110 also include front tips 122. Straps 118are coupled to cross shafts 112 and 116 to limit the travel of lowerrails 110 relative to cross bar 116. Front and rear wheels 113 arecoupled to lower rails 110. Wheels 113 contact a portion of belt 144between wheels 113 and lower rails 110 to maintain the proper alignmentof belt 144 at it rotates around endless belt assembly 12.

Drive system 124 includes shaft 126 which includes splined section 130and splined section 128. Splined section 130 receives power from themotor and transmission of snowmobile 10 to rotate shaft 126. Splinedsection 128 engages sprockets 132, 136 and 140 which engage belt 144 asshown in FIGS. 22-25. Referring now to FIGS. 21 and 22, sprockets 132,136 and 140 are positioned on shaft 126 at a position substantially inbetween front tips 122 of rails 110. Sprocket 132 includes a pluralityof lateral extensions 134 positioned around its outer circumference.Similarly, sprocket 140 includes a plurality of lateral extensions 142positioned around its outer circumference. Sprockets 132 and 140 have aninvolute orientation. Sprocket 136 is positioned between sprocket 132and 140 and includes a plurality of circumferentially extendingprojections 138. Sprocket 136 has a convolute orientation. Shaft 126also defines laterally extending axis 133. Theoretical cylindricalvolume 131 is defined by axis 133 and diameter 135, which is equal tothe diameter of sprocket 140. Cylindrical volume 131 extends laterallyfrom drive system 124. During movement of endless belt assembly 12, suchas during a jounce event, lower rails 110 may move upward or forward toa position in which front tips 122 of lower rails 110 intersectcylindrical volume 131. In this embodiment, drive system 124 includesthree sprockets, however, any suitable number of sprockets and anysuitable combination of involute and convolute orientation may be used.

Referring now to FIGS. 23 and 24, a profile view of endless beltassembly 12 is shown. As discussed above, circumferentially extendingprojections 138 of sprocket 136 engage apertures 146 in belt 144. Belt144 also includes apertures 149, rows of outer teeth 147 and rows ofinner teeth 145. Lateral extensions 134 and 142 of sprockets 132 and 140engage rows of inner teeth 145 of belt 144. Rows of outer teeth 147 ofbelt 144 are positioned between lower rails 110 and idler pulleys 144 tomaintain belt 144 in the proper orientation. Apertures 149 permit snowand ice to contact lower rails 110 to provide cooling and lubrication.

As shown in FIG. 23, lower rails 110 also include rear sections 148.Rear sections 148 of lower rails 110 include upward draft 149. In thisembodiment, upward draft 149 is about three degrees, however anysuitable amount of upward draft may be used on lower rails 110. In thisembodiment, rear wheels 113 are located at the point at which upwarddraft 149 begins, however rear wheels 113 may be located at any suitableposition. Handling and ride characteristics of snowmobile 10 may improvewhen rear wheels 113 are positioned within one radius of the beginningof upward draft 149. For example, if rear wheels 113 have a radius of 4inches and upward draft 149 begins 12 inches from the end of lower rails110, it may be beneficial to position rear wheels 113 between 10 and 14inches from the rear end of lower rails 110. It should also be notedthat positioning rear wheels 113 within one radius of the beginning ofupward draft 149 may improve handling characteristics of snowmobile 10when rear idler pulleys 150 are positioned between lower rails 110rather than on the outer surface of lower rails 110 similar to wheels113.

Referring now to FIG. 26, rear sections 144 of lower rails 110 is shown.Idler pulleys 150 are positioned between lower rails 110 on cross shaft152. Idler pulleys 150 are positioned between plurality of innerprojections 145 on belt 144 to provide the appropriate tension to belt144 and maintain proper orientation of belt 144 during movement.

Referring now to FIGS. 27 and 28, air intake system 152 is shown. Airintake system 152 is positioned under hood 16 of snowmobile 10. Airintake system 152 includes air intakes 154, ducts 156, expandablesection 158, lower duct 164, upper duct 176 and plenum 184. Air inlets154 each include screen 160 and air collector 162. Screens 160 arepositioned on hood 16 of snowmobile 10 to direct incoming air throughair collectors 162 into ducts 156. Referring to FIG. 30, expandablesection 158 is shown in the stationary position, with hood 16 in thedefault position, and in the raised position in phantom, with hood 16raised.

Referring now to FIG. 29, air from ducts 156 enters expandable section158 which is coupled to lower duct 164. Expandable section 158 ispositioned in opening 166 of lower duct 164. Lower duct 164 includesopening 168 and end 170. Opening 168 supports nozzle 190 and Helmholtzbox 192. Screen 172 and resonator 174 are positioned in end 170 of lowerduct 164. Upper duct 176 couples to end 170 of lower duct 164 to encloseresonator 174 and screen 172. Upper duct 176 includes curved portion 179and end 180. Curved portion 179 includes aperture 178 which includesseal 194 and Helmholtz box 196. End 180 is coupled to seal 182 andplenum 184. Plenum 184 includes two outlets 186 which each include seals188. Seals 188 are coupled to an intake manifold of the motor ofsnowmobile 10. Helmholtz boxes 192 and 196 cooperate with resonator 174to reduce the noise of incoming air. Helmholtz boxes 192 and 196 may beadapted to tune incoming air to a pre-determined frequency that issuppressed by resonator 174 to reduce the noise generated by air intakesystem 152. For example, in a test snowmobile, the Helmholtz boxes andresonator were tuned to remove frequencies at 250, 500, and 750 Hertz.Helmholtz resonator's are designed and optimized by changing the volumeof the plenum as well as the neck length and diameter to target aspecific frequency. The frequency of attenuation of resonator 174 is afunction of the whole size and spacing. Air intake system 152 includes aplurality of seals between the ducts to create a sealed system, therebydecreasing the likelihood of heating the air carried by air intakesystem 152 before it reaches the motor of snowmobile 10.

Referring now to FIGS. 31 and 35, left front ski 18 of snowmobile 10 isshown. Steering arm 223 of snowmobile 10 couples to front ski 18 atfirst position 208 of ski 18. Ski 18 includes a body portion having afront end 206 and a rear end 204. Front end 206 includes hoop 200. Theupper surface of ski 18 includes a plurality of projections 202 that areformed within the upper surface to provide traction to an operator whomay stand on ski 18. In the illustrated embodiment, a plurality ofprojections 202 are arranged side by side on top surfaces or top edgesof longitudinally extending ribs 203. Ribs 203 extend vertically fromthe upper surface of the ski 18. Therefore, a plurality of projections202 are arranged in longitudinally extending rows as shown in FIGS. 31and 35, for example. First and second outer ribs 209 and 211 are locatednear inner and outer edges 213 and 215, respectively, of the ski asshown in FIG. 35. The first and second ribs 209 and 211 each include aplurality of projections 203 arranged side by side on top edges thereof.A plurality of inner projections 203 extend upwardly from the uppersurface of the ski and are located between the first and second ribs 209and 211. Some inner projections 203 are located on top edges of innerribs 225 located between the first and second outer ribs 209 and 211.Other inner projections 227 are located on the upper surface of the ski18 between the first and second ribs 209 and 211.

Referring now to FIGS. 32-34, a profile and bottom side view of ski 18is shown. The bottom surface 201 of ski 18 includes keel 212 and runner210. As shown in FIG. 34, bottom surface 201 is a planar surface. Runner210 is supported by keel 212. Keel 212 includes front end 216 and rearend 214. Keel 212 extends longitudinally along the bottom side of ski 18a length L. In this embodiment, at least 60% of the length L of keel 212is in front of (in FIG. 32, to the left of) first position 208 whichmounts to steering arm 22. In this embodiment, the ratio of the width ofthe middle of keel 212 to the width of runner 210 is about 4.3, howeverany suitable ration may be used.

As shown in FIG. 33, in this embodiment, rear end 214 of keel 212 is thewidest portion of keel 212. Rear end 214 is substantially wider thanfront end 216 or any other portion of keel 212. In this embodiment, ski18 is constructed of a plastic material and runner 210 is constructed ofa metallic material, however any suitable material may be used toconstruct front ski 18 and runner 210.

Another embodiment of a front ski that may be used on snowmobile 10 isshown in FIG. 36. Front ski 217 may be coupled to steering arm 22 oneither the left or right side of snowmobile 10. Ski 21 includes a bodyportion having a front end 219, a middle portion 220 and a rear end 218.Outer edge 221 of ski 217 includes a laterally recessed or notchedportion 222 on rear end 218 of ski 217. In this embodiment, rear end 218is substantially narrower than middle portion 220 of ski 217. Notchedportion 222 of edge 221 may provide superior handling in certainconditions. As shown in FIG. 36, the ski 217 has on overall lengthdimension 230. Illustratively the notched portion 222 is formed in thebody portion having the planar bottom surface 201. Notched portion 222has a length dimension 232 which is preferably about one fifth (⅕) ofthe overall ski length dimension 230. Middle portion 220 of ski 217 hasa width dimension 234. The notched portion 222 has a width dimension of236 which is preferably about one fourth (¼) of the ski width dimension234. Therefore, the narrower rear end 218 of ski 217 has a widthdimension 238 which is illustratively about three fourths (¾) of theoverall ski width dimension 234 at the middle portion 220 of the ski217. This notch size balances maintaining ski floatation with theimproved handling feature provided by the notched portion 222.

The length of notched portion 222 illustrated by length dimension 232illustrating ranges from about one sixth (⅙) to about one half (½) ofthe length dimension 230 of the ski 217. As discussed above, one fifth(⅕) is the preferred length ratio. In other illustrative embodiments,the length dimension 232 is one sixth (⅙), one fourth (¼), one third (⅓)or one half (½) of the ski length dimension 230, for example.

Likewise, the width dimension 236 of notched portion 222 illustrativelyranges from about one fifth (⅕) to about one half (½) of the widthdimension 234 of ski 217. As discussed above, one fourth (¼) is thepreferred width ratio.

Another embodiment of a front ski that may be used on snowmobile 10 isshown in FIG. 37. Front ski 362 may be coupled to steering arm 22 oneither the left or right side of snowmobile 10. Ski 362 includes frontend 365, middle portion 363 and rear end 364. Outer edges 366 and 368 ofski 362 each include a laterally recessed or notched portion 366 and368, respectively, on rear end 364 of ski 362. In this embodiment, rearend 364 is substantially narrower than middle portion 363 of ski 362.Notched portions 366 and 368 may provide superior handling in certainconditions. As shown in FIG. 37, the ski 362 has on overall lengthdimension 370. Notched portions 366 and 368 each have a length dimension372 which is about one fifth (⅕) of the overall ski length dimension370. Middle portion 363 of ski 362 has a width dimension 374. Thenotched portions 366 and 368 each have a width dimension of 376 which isillustratively about one fourth (¼) of the ski width dimension 374.Therefore, the narrower rear end 364 of ski 362 has a width dimension378 which is illustratively about one half (½) of the overall ski widthdimension 374 at the middle portion 363 of the ski 362. The sizes ofnotched portions 366 and 368 may vary as discussed above with regard tonotched portion 222.

While this invention has been described as having an exemplary design,the present invention may be further modified within the spirit andscope of this disclosure. This application is therefore intended tocover any variations, uses, or adaptations of the invention using itsgeneral principles. Further, this application is intended to cover suchdepartures from the present disclosure as come within known or customarypractice in the art to which this invention pertains.

1-8. (canceled)
 9. A snowmobile comprising: a frame including side wallsand a support platform, the side walls cooperating with the supportplatform to define a tunnel; an endless belt assembly supported by theframe; a motor supported by the frame; and a running board removablycoupled to the tunnel.
 10. The snowmobile of claim 9, further comprisinga tube member positioned laterally outward from the running board andremovably coupled to the tunnel.
 11. The snowmobile of claim 10, whereinthe tube member has a forward end with a first flange and rearward endwith a second flange, and the second flange is removably coupled to theside wall.
 12. The snowmobile of claim 11, further comprising a footgrip assembly, and a portion of the foot grip assembly is removablycoupled to the first flange.
 13. The snowmobile of claim 12, wherein thefoot grip assembly includes an upper member, a lower member, a toe clip,and a frame member, and the lower member is removably coupled to therunning board.
 14. The snowmobile of claim 9, further comprising a footgrip assembly removably coupled to the frame and the running board. 15.The snowmobile of claim 9, further comprising a longitudinal tube memberpositioned laterally outward from the running board assembly andremovably coupled to the tunnel, and a foot grip assembly removablycoupled to the tube member.
 16. The snowmobile of claim 15, wherein thefoot grip assembly extends above the support platform.
 17. A snowmobilecomprising: a frame including side walls and a support platform, theside walls cooperating with the support platform to define a tunnel; anendless belt assembly supported by the frame; a motor supported by theframe; a running board removably coupled to the tunnel; and a foot gripassembly removably coupled to the running board assembly.
 18. Thesnowmobile of claim 17, wherein the foot grip assembly includes an uppermember, a lower member, a toe clip, and a frame member, and the lowermember is removably coupled to the running board.
 19. The snowmobile ofclaim 18, wherein the toe clip extends rearwardly from the upper member,the lower member, and the frame member.
 20. The snowmobile of claim 18,wherein an upper end of the upper member is removably coupled to theframe member.
 21. The snowmobile of claim 18, wherein the running boardextends forwardly beyond the foot grip assembly.
 22. The snowmobile ofclaim 17, further comprising a plurality of upstanding members flankingthe frame and the foot grip assembly is coupled to the upstandingmembers.
 23. A snowmobile comprising: a frame including side walls and asupport platform, the side walls cooperating with the support platformto define a tunnel; an endless belt assembly supported by the frame; amotor supported by the frame; a running board removably coupled to thetunnel along an inner side of the running board; a foot grip assemblyremovably coupled to a forward portion of the running board assembly;and a longitudinally-extending tube member coupled to the running boardalong an outer side of the running board.
 24. The snowmobile of claim23, wherein the foot grip assembly includes an upper member, a lowermember, a toe clip, and a frame member, and the lower member isremovably coupled to the running board.
 25. The snowmobile of claim 24,further comprising a steering hoop positioned at a forward end of thesupport platform, and the frame member is coupled to the steering hoop.26. The snowmobile of claim 24, wherein an upper end of the upper memberis removably coupled to the frame member.
 27. The snowmobile of claim23, wherein the running board extends forwardly beyond the foot gripassembly.
 28. The snowmobile of claim 23, wherein thelongitudinally-extending tube member has a forward end with a firstflange and rearward end with a second flange, the first flange isremovably coupled to the foot grip assembly and the second flange isremovably coupled to the side wall.
 29. The snowmobile of claim 23,wherein the longitudinally-extending tube member is removably coupled tothe running board.
 30. The snowmobile of claim 23, further comprising anair intake system operably coupled to the motor and adapted to supplyair to the motor, the air intake system including a Helmholtz box.